There has hitherto been conceived an optical device having a laser light emitting portion which emits laser light, a polygon mirror which includes a reflective surface for reflecting the laser light and which is driven to rotate, thereby to deflect the laser light emitted from the laser light emitting portion and to scan a scanned surface, a first lens through which the laser light reflected by the polygon mirror is transmitted and which refracts the laser light along the scanned surface, and a second lens through which the laser light having passed through the first lens is transmitted and which refracts the laser light along the scanned surface. In the optical device of this type, the laser light emitted from the laser light emitting portion can be deflected by the polygon mirror so as to scan the scanned surface, and it can be further refracted along the scanned surface through the first and second lenses.
It has also been proposed to enhance an fθ characteristic (so-called “linearity”) by adopting an anamorphic aspheric surface for the first lens, and a two-dimensional polynomial aspheric surface for the second lens (refer to, for example, JP-A-2003-149573).